Anime based on light novel tend to have a strong pre - existing fan base from the light novel readers. This can influence the popularity and the marketing of the anime. For example, the hype around an anime like 'A Certain Magical Index' was partly due to the large number of light novel fans waiting for its adaptation. In terms of story content, they often carry the unique narrative styles of the light novel authors. Some light novel - based anime have a very internal monologue - heavy style, like in 'The Melancholy of Haruhi Suzumiya' where Haruhi's thoughts and actions are often accompanied by her own internal musings. This is not as common in other types of anime. Additionally, the world - building in light - novel - based anime is often more elaborate as it has been developed in the written form first, such as the complex magic and technology systems in 'Log Horizon'.
Well, one major difference is the pacing. Anime based on light novel might follow the pacing of the novel more closely in the early episodes. This means that sometimes they can be a bit slow - paced as they are trying to set up the complex world and introduce numerous characters. In contrast, some original anime can be more free - form in their pacing. Also, the character designs in light - novel - based anime are often very faithful to the original illustrations in the novels. For instance, in 'Re:Zero - Starting Life in Another World', the look of Subaru and Emilia is very much in line with how they were depicted in the light novel. This is not always the case with non - light - novel - based anime where character designs can be more experimental. Moreover, the themes explored in light - novel - based anime can be more directly related to the themes in the original novels, like the exploration of power and morality in 'Overlord'.